Refine
Labor/Institute
- Kompetenzzentrum Künstliche Intelligenz (36)
- Angewandte Lasertechnik und Photonik (alp) (34)
- BIOMEMS Lab (33)
- ZeWiS (23)
- Internationales Technisches Vertriebsmanagement (Bachelor) (22)
- Betriebswirtschaft und Recht (Bachelor) (16)
- Behavioral Accounting & Finance Lab (13)
- Elektro- und Informationstechnik (Bachelor) (13)
- Information Management Institut (12)
- Embedded Systems (11)
Keywords
- Fahrerassistenzsystem (69)
- Spiegelteleskop (48)
- Neuronales Netz (37)
- Femtosekundenlaser (36)
- Bragg-Reflektor (33)
- Iridium (31)
- Fußgänger (30)
- Mikroelektrode (29)
- X-ray (29)
- mirror (29)
Year of publication
Document Type
- Article (478)
- Conference Proceeding (472)
- Book (66)
- Other (66)
- Part of a Book (49)
- Working Paper (45)
- Doctoral Thesis (30)
- Patent (23)
- Report (19)
- Preprint (5)
Language
- English (760)
- German (487)
- Multiple languages (4)
- Spanish (2)
- French (1)
Global Remote Events (GRE) in Science & Higher Education (HE) with a Focus on Intercultural Aspects
(2022)
Der Vorschlag einer drastischen Erhöhung des Mindestreservesatzes durch die EZB erhitzt die Gemüter. Nach teils heftiger Kritik hochrangiger Bankenvertreter in Deutschland werden die „üblichen“ Beschuldigungen vorgebracht und von Medien z.T. unreflektiert wiedergegeben bzw. kommentiert. Die Banken erhielten seit Herbst 2022 – so das gängige Muster - risikolose und ungerechte Subventionen und wüssten nichts Besseres mit ihren Einlagen bei der Bundesbank anzufangen.
Diese Kritik greift zu kurz und ist teils sachlich falsch.
Progress in satellite control engineering enables tandem flight arrangements of mini-satellites in future space missions. Cost effective CubeSat technologies offer an interesting possibility for space-born telescope payloads. Two small satellites will carry the telescope optics and the detector system, respectively. Related formation flight requirements could be transferred from the NetSat-Mission.
Objective. Schizophrenia (SCZ) is a severe mental disorder associated with persistent or recurrent psychosis, hallucinations, delusions, and thought disorders that affect approximately 26 million people worldwide, according to the World Health Organization. Several studies encompass machine learning (ML) and deep learning algorithms to automate the diagnosis of this mental disorder. Others study SCZ brain networks to get new insights into the dynamics of information processing in individuals suffering from the condition. In this paper, we offer a rigorous approach with ML and deep learning techniques for evaluating connectivity matrices and measures of complex networks to establish an automated diagnosis and comprehend the topology and dynamics of brain networks in SCZ individuals. Approach. For this purpose, we employed an functional magnetic resonance imaging (fMRI) and electroencephalogram (EEG) dataset. In addition, we combined EEG measures, i.e. Hjorth mobility and complexity, with complex network measurements to be analyzed in our model for the first time in the literature. Main results. When comparing the SCZ group to the control group, we found a high positive correlation between the left superior parietal lobe and the left motor cortex and a positive correlation between the left dorsal posterior cingulate cortex and the left primary motor. Regarding complex network measures, the diameter, which corresponds to the longest shortest path length in a network, may be regarded as a biomarker because it is the most crucial measure in different data modalities. Furthermore, the SCZ brain networks exhibit less segregation and a lower distribution of information. As a result, EEG measures outperformed complex networks in capturing the brain alterations associated with SCZ. Significance. Our model achieved an area under receiver operating characteristic curve (AUC) of 100% and an accuracy of 98.5% for the fMRI, an AUC of 95%, and an accuracy of 95.4% for the EEG data set. These are excellent classification results. Furthermore, we investigated the impact of specific brain connections and network measures on these results, which helped us better describe changes in the diseased brain.
Manipulation von Abgaswerten
(2023)
Dieses kleine Buch stellt Hintergründe zum Abgasskandal dar, z. B. welche Schadstoffe kritisch sind, wie Motorsteuergeräte, Abgasrückführung und Abgasnachbehandlung funktionieren, wie Manipulationen auf dem Prüfstand möglich sind, mit welchen Fahrzyklen getestet wird und in welchem rechtlichen und politischen Umfeld dies lange Zeit unbemerkt mit unterschiedlichen Konsequenzen in der EU und den USA geschehen konnte. Es werden Maßnahmen vorgestellt, mit denen Fahrzeuge auch real gesetzliche Grenzwerte einhalten können und wie Manipulationen zukünftig rechtlich und politisch verhindert werden können. Dem Leser werden durch Literaturhinweise zusätzliche Details erschlossen.
Die voranschreitende Digitalisierung und insbesondere der Einsatz von Künstlicher Intelligenz (KI) in der
Bildung eröffnen neue Möglichkeiten des Lernens. Bildung kann stärker individuell sowie zeitlich und
räumlich entgrenzt stattfinden. ChatGPT verdeutlicht, wie dynamisch die Entwicklungen im Bereich KI
sind. Das in Zunahme begriffene Interesse am Thema KI allgemein sowie KI in der Bildung kommt dem
erforderlichen Austausch zwischen zentralen Akteur:innen zugute. Dieses Diskussionspapier präsentiert
drei Zukunftsszenarien für den Einsatz von KI in der institutionellen Bildung: Hochschule, Weiterbildung
und Schule. Im Fokus stehen die übergeordneten Fragestellungen nach Voraussetzungen und
Gelingensbedingungen einer erfolgreichen Anwendung sowie nach gemeinsamen Handlungsfeldern
für zentrale Stakeholder. Fünf Handlungsfelder für den Einsatz von KI in institutioneller Bildung sind auf
Grundlage der skizzierten Zukunftsszenarien hervorzuheben: (1) Interdisziplinäre Zusammenarbeit, (2)
Qualifizierungsangebote und Kompetenzentwicklung, (3) Digitale Infrastruktur und Personal, (4) Ethik
und Datensouveränität sowie (5) Interoperabilität von Daten in Bildungskontexten. Ziel des
vorliegenden Diskussionspapiers ist es, den kooperativen Austausch zwischen relevanten Stakeholdern
anzuregen.
The following contribution deals with the environmental conditions of highly gifted and
sensitive people (HGSP). Three researchers from different perspectives (physics, pedagogy,
and innovation management) empathize with the target group and try to understand their
experiences. From three interviews with adults, a first point of view is defined adopting the
Grounded Theory methodology. Adult interviews are compared with the perceptions of an
adolescent from today moving between state and private education systems. By comparing
both perspectives, differences and similarities are worked out. The discussions are used to
develop an online test focusing on creativity, motivation for achievement, and cognitive
capacities, as these are core categories identified that seem to be highly important in
combination. The empirical test is intended to provide the state education system with a simple
and interactive solution to identify a large group of people who need further support. To
achieve a high participation rate, the test will be designed for a maximum of one hour and the
implementation and evaluation will be carried out digitally. The authors' vision is to create an
adaptive environment that can effectively adjust to and educate diverse groups of learners
without over- or under burdening teachers and learners. A key finding of our case-based
research is that the existing school and higher education structures are not able to provide
sufficient support and challenge for HGSP. Support measures for HGSP are needed as well
as a new understanding of learning and teaching, so that new competencies can be built that
consider people's self-regulation, creativity, and motivation for achievement, in addition to
cognition and meta-cognition. Kuhl (2004, 18) explains why the capacities of self-regulation
are paramount for highly gifted students. When they want to meet a challenge, they face
problems that are more difficult and therefore need more persistence, resilience, and selfmotivation. However, to support these special needs, teachers are often not ready or capable
to do so, nor do these needs fit with the performance requirements of the regular curriculum.
Circular Innovator Education
(2021)
The following article is a first step towards raising the awareness of these new trainers (who are conscious and innovators themselves) and giving them methods, tools, and inspiration to develop sustainable innovators to think holistically. Innovators are the proportion of entrepreneurs who do not copy or optimize what already exists but commercialize new technologies or new ideas. Circular innovators are the doers who create systemic innovations solving our current social and ecological crisis.
In this chapter, the EIL (Effective Innovation Leadership) framework is tested empirically. First, peer-reviewed journals in the innovation management, leadership, and transformation discipline are analyzed. Second, a pre-test with 58 executives takes place. The response behavior of the participants varies depending on the company's degree of digital maturity. Third, 20 innovation leaders employed in mature digital companies answer the survey. The participants perceive their company as innovative and state that up to 89% of created innovations are digital. Values relevant to digital innovation leaders are innovation, responsibility, positivity, and transparency. Relevant strengths are creativity and learning. Both strongly correlate with a few efficacy items. Decisiveness correlates with innovation strategy. Entrepreneurship, self-regulation, and culture correlate with each other. Creativity connects the value of innovation and the practice of communication. The insights from this chapter contribute to building a reliable and valid factor-based effective digital innovation leadership questionnaire in the future.
Application of the Effective Innovation Leadership Model in a Digital Innovation Project: Case Study
(2020)
Germany has become sedate and partially missed digital opportunities generating value. Since 1995, the term innovation leadership is getting increasing attention. Still, there exists no clear definition. The effective innovation leadership (EIL) model resulted from a Ph.D. thesis and is grounded in the iteration of six data sets. It has been used in industry since 2014. This chapter examines the application of the EIL model in one German middle-class enterprise in 2018/2019. Core challenges in the systemic context, which hinder the effectiveness of innovation leadership in the organizational context, are the support of people across functions and hierarchies as well as inflexible structures and digital access. Especially negative pressure coming from an overvaluation of the shareholder, egos fighting for power, extensive drama triangular, fixed mindsets, and freeloaders hinder the effectiveness of innovation leadership. A comparison of the EIL model with rival theory shows that innovation leadership is close to entrepreneurial approaches and an integral part of innovation management.
Das RöLab versteht sich als ein überregionales, außerschulisches Bildungsangebot, das Begeisterung für Natur- und Ingenieurwissenschaften, Medizin und Medizintechnik an unterschiedliche Zielgruppen vermittelt und damit einen Beitrag zur Allgemeinbildung und MINT-Förderung leistet. Das didaktische Konzept nimmt den „Hands-on-Science“ Gedanken stringent auf, weckt den Forschergeist und ermöglicht es den Lernenden, Unsichtbares zu erkunden.
2023 jährte sich der Todestag von Wilhelm Conrad Röntgen zum einhundertsten Mal. Im Jahr 1895 entdeckte er eine neue Art von Strahlung, die feste Materialien durchdringen kann. 1901 erhielt er für diese Entdeckung den ersten Nobelpreis für Physik. Das Deutsche Röntgen-Museum erforscht und dokumentiert das Leben und Werk von W. C. Röntgen und die Auswirkungen seiner Entdeckung.
Conventional mining might not be sufficient to support the growth of humankind which is heavily dependent upon rare materials in technical applications. Asteroid mining might be an answer, with Near-Earth objects (NEOs) being the first targets. However, the first step in the asteroid mining cascade is to probe reachable
asteroids. Moreover, to identify the best candidates for further activities hundreds to thousands of asteroids must be screened. The fast progressing development of CubeSats might allow the space community to do the initial in-situ screening in a minimalistical and economical manner. Additionally, formation flying might enable the miniaturization of optical payloads for asteroid composition analysis in CubeSats. The recent developments in formation flying are summarised in this study and the possibility of utilizing formation flying CubeSats for
asteroid surveillance explored.
Starting in 1951, the 50th anniversary of the award of the first Nobel Prize for physics to Wilhelm Conrad Röntgen, the Lord Mayor of the German City of Remscheid has given out Röntgen Medals. The Röntgen Medal annually honours
scientists who "in the broadest sense have made a special contribution to the progress and dissemination of X-ray
discoveries in the theoretical and applied sciences". The Röntgen Medal has become highly recognized in the scientific world. To date, more than one hundred excellent scientists have received the honour. Through their chronology, this
contribution presents a "Who’s Who" of X-ray science and provides selected insights into their scientific work; with the fields of X-ray optics and X-ray astronomy receiving special focus.
In 1895, Professor Wilhelm Conrad Röntgen detected a new type of radiation that was able to penetrate solid materials, which he called X-rays. In 1901 Röntgen received the first Nobel Prize in physics in honour of this ground breaking
discovery. The Deutsches Röntgen-Museum (DRM) in Remscheid (Germany) is the institution that uniquely and
comprehensively explores and documents the life and work of W. C. Röntgen and the impact of his discovery. The DRM’s
location in Remscheid is not coincidental, with Röntgen’s birthplace only a short walk away from the exhibits. Every visit to the museum amounts to a unique expedition through the worlds of medicine, science and technology. The museum’s emphasis on the diversity of Röntgen’s invention by a multilingual, multi-medial approach enables all visitors to make their own personal discoveries. The Deutsches Röntgen-Museum in Remscheid is a must-see for X-ray scientists from anywhere in the world. This contribution provides an insight into the history of X-rays and offers a guided tour of the Deutsches Röntgen-Museum and its exhibits.
In this article, we contribute to the longstanding debate among economists regarding the question of “nature or nurture” with respect to economics students’ attitudes toward various allocation mechanisms for a scarce resource. While previous research starts the debate by beginning with first-year economics students, we aim to evaluate pre-firstyear individuals, i.e., school pupils. Drawing on the seminal works of Haucap, J., & Just, T. (2010). Not guilty? Another look at the nature and nurture of economics students. European Journal of Law and Economics, 29(2), 239–254 and Frey, B. S., Pommerehne,W.W., & Gygi, B. (1993). Economics indoctrination or selection? Some empirical results. The Journal of Economic Education, 24(3), 271–281, we investigate a sample of pupils ranging from the 5th to the 13th grades to determine whether pupils are “born economists” (nature), develop economic thinking (nurture), or both. We find that young individuals start to think differently in early grades and that their thinking and attitudes are shaped differently throughout their school careers, thereby providing support for the effects of both nature and nurture. Our findings show that school time impacts fairness judgments, particularly regarding price mechanisms. Regarding learning or indoctrination, we find that economics-inclined pupils are positively affected by lessons in economics in school, while pupils who are economics-averse draw completely diametric conclusions from economics lessons, thereby exhibiting increased disapproval of price allocation over the course of these classes and increased approval of the first come, first served and governmental action mechanisms.Moreover, we find strong effects of gender and migration background in this context. This study is the first to elucidate the development of economic thinking in 5th–13th grade pupils. Our results are important for economists, educators,
and researchers because they can serve as a starting point for subsequent investigations in this under-researched field.
Evaluating the impact of deviating technical standards on business processes, trade and innovation
(2023)
Surrounding the increasingly intense discussions about the emergence of new global standardization regimes in context of China’s rise as a dominant standardization power, there has been much talk about countries purposefully using deviating national standards to impose trade barriers. The discussion of whether and to what degree technical standards deviate from international standards and how this affects business, trade, innovation and the standard system is of global relevance. As research about the impact of deviating technical standards is still strongly underrepresented in the academic community, this research analyses the different “degrees” of deviation and the respective impact of minor or negligible deviation and strong deviation on businesses trading in a global context. By using a mixed research method based on literature review, analysis of standard documents and semi-structured interviews, this study discusses peculiarities and challenges associated with deviating technical standards. This is of relevance with regards to international trade and especially trade with countries that became increasingly important players in the international standardization regime. Our research will therefore add further insights to a better understanding of the close linkage between economic growth and standardization. This paper further highlights how deviating technical standards impact companies around the globe and how these companies could use a newly developed risk indicator to not only engage in the standard game but also to better assess consequences.
Due to the recent progress in satellite control engineering, tandem flight arrangements of mini-satellites are currently in discussion and
under consideration for future space missions. CubeSat technologies offer an interesting possibility for space-born telescope payloads
based on this approach. In such a scenario, two small satellites will fly at a constant distance of a few meters up to 100 meters. Thereby,
the front satellite will carry the telescope optics and the second satellite the detector system. Related formation flight requirements were
addressed in the NetSat-Mission, composed of four 3U-CubeSats, launched 2020. Space technology challenges concern in particular orbit
control by an appropriate propulsion system as well as precision attitude pointing towards the joint target, and could be transferred from the
NetSat-mission to the proposed Tandem Mission. This will allow space-based telescopes with a long focal length even placed on board of
small or miniature CubeSat-type satellites. Cost effective Kirkpatrick-Baez type X-ray telescopes represent an important application here as
they have longer focal lengths compared to previous astronomical observatories using Wolter I type X-ray mirrors.
In diesem Jahr jährte sich der Todestag von Wilhelm Conrad Röntgen, gestorben am 10. Februar 1923, zum hundertsten Mal. Dieser Beitrag ist eine Hommage auf diesen bedeutenden deutschen Wissenschaftler. 1895 entdeckte er eine neue Art von Strahlung, welche in der Lage ist, feste Materialien zu durchdringen. 1901 erhielt Professor Röntgen für diese bahnbrechende Entdeckung den ersten Nobelpreis für Physik. Das Deutsche Röntgen-Museum (DRM) erforscht und dokumentiert das Leben und Werk von W. C. Röntgen und die Auswirkungen seiner Entdeckung auf eine einzigartige und umfassende Weise. Der Standort des DRM in Remscheid ist kein Zufall, denn Röntgens Geburtshaus liegt nur wenige Gehminuten von den Exponaten entfernt. Die Betonung der Vielfalt von Röntgens Erfindung durch das Museum mit einer multimedialen Herangehensweise ermöglicht es den Besuchern, hier ihre ganz persönlichen Entdeckungen zu machen. Jeder Museumsbesuch wird so zu einer einzigartigen Entdeckungsreise durch die Welt der Medizin, Wissenschaft und Technik. Dieser Beitrag würdigt das Lebenswerk von Professor Wilhelm Conrad Röntgen und gibt einen Einblick in die Geschichte der Röntgenstrahlen und ihre Anwendungsgebiete.
„Freude habe ich nur, solange ich es mit dem Experimentieren zu tun habe“, schrieb Wilhelm Conrad Röntgen am 9.6.1920 an Margret Boveri. Das Deutsche Röntgen-Museum und das Remscheider Röntgengymnasium geben getreu diesem Motto Kindern und Jugendlichen die Möglichkeit, selbst aktiv zu werden, zu experimentieren und so auf den Spuren dieses bedeutenden Forschers zu wandeln. Hierzu wurde am 8. November 2011, einem Jahrestag der Entdeckung der Röntgenstrahlen, das Museumslabor RöLab gegründet. Dort werden Themenbrücken in das tägliche Leben geschlagen und so Lernprozesse im MINT-Bereich für die jungen Forschenden anregend, attraktiv und nachhaltig erlebbar. Das RöLab versteht sich als ein überregionales, außerschulisches Bildungsangebot, das Begeisterung für Natur- und Ingenieurwissenschaften, Medizin und Medizintechnik an unterschiedliche Zielgruppen vermittelt und damit einen Beitrag zur Allgemeinbildung und MINT-Förderung leistet. Das didaktische Konzept nimmt den „Hands-on-Science“ Gedanken stringent auf, weckt den Forschergeist und ermöglicht es den Lernenden, Unsichtbares zu erkunden. Dieser Beitrag stellt das Museumslabor RöLab des Deutschen Röntgen-Museums vor.
Diagnosis of autism spectrum disorder based on functional brain networks and machine learning
(2023)
Autism is a multifaceted neurodevelopmental condition whose accurate diagnosis may be challenging because the associated symptoms and severity vary considerably. The wrong diagnosis can affect families and the educational system, raising the risk of depression, eating disorders, and self-harm. Recently, many works have proposed new methods for the diagnosis of autism based on machine learning and brain data. However, these works focus on only one pairwise statistical metric, ignoring the brain network organization. In this paper, we propose a method for the automatic diagnosis of autism based on functional brain imaging data recorded from 500 subjects, where 242 present autism spectrum disorder considering the regions of interest throughout Bootstrap Analysis of Stable Cluster map. Our method can distinguish the control group from autism spectrum disorder patients with high accuracy. Indeed the best performance provides an AUC near 1.0, which is higher than that found in the literature. We verify that the left ventral posterior cingulate cortex region is less connected to an area in the cerebellum of patients with this neurodevelopment disorder, which agrees with previous studies. The functional brain networks of autism spectrum disorder patients show more segregation, less distribution of information across the network, and less connectivity compared to the control cases. Our workflow provides medical interpretability and can be used on other fMRI and EEG data, including small data sets.
A novel 3D-printed glucose sensor is presented for cell culture application. Glucose sensing was performed using a fluorescence resonance energy transfer (FRET)-based assay principle based on ConA and dextran. Both molecules are encapsulated in alginate microspheres and embedded in the UV-curable, stable hydrogel polyvinyl alcohol (PVA). The rheology of the formulation was adapted to obtain good properties for an extrusion-based printing process. The printed sensor structures were tested for their ability to detect glucose in vitro. A proportional increase in fluorescence intensity was observed in a concentration range of 0 - 2 g/L glucose. Tests with HEK cell cultures also showed good cell compatibility and excellent adhesion properties on plasma-treated Petri dishes. The printed sensors were able to detect the glucose decay associated with the metabolic activities of the fast-growing HEK cells in the cell culture medium over ten days. The proof-of-principle study shows that metabolic processes in cell cultures can be monitored with the new printed sensor using a standard fluorescence wide-field microscope.
While Bragg grating-based optical devices have shown promising performances for pressure sensing applications, their sensitivity, especially in the low-pressure regime, is unsatisfying and needs to be optimized by elaborate designs, such as cantilevers or other extrinsic mechanical transducers. This contribution demonstrates and discusses a novel concept for optical pressure sensors based on polymer planar Bragg gratings. Waveguide and Bragg grating are fabricated underneath the surface of a temperature-stable and humidity-insensitive cyclic olefin copolymer substrate by means of a femtosecond laser. Based on the employed direct-writing procedure, in combination with adaptive, in-situ beam shaping with a spatial light modulator, writing depth, i.e., location of the photonic structures within the substrate, as well as Bragg grating periodicity and positioning can be deliberately chosen. Afterwards, the polymer substrate is post-processed with a high-precision micro mill, so a diaphragm comprising the integrated photonic structures is generated. The resulting diaphragm exhibits a thickness of 300 µm and a diameter of 10 mm. Finally, the optical sensor is packaged and sealed to form an air-filled gas pocket underneath the diaphragm. Deformations of the diaphragm by external pressure changes translate to strain variations along the waveguide axis and thus perturb the Bragg grating period. This leads to changes in the grating’s wavelength of main reflection, which can be evaluated in order to quantify the relative external pressure. With this straightforward optical sensor concept, pressure sensitivities up to 39 pm kPa-1, within relative pressures ranges from 78 kPa to 372 kPa, are achieved.
While sapphire is one of the most durable materials, its properties entail that high-precision machining, especially in the sub-millimeter regime, is still challenging. This contribution demonstrates and discusses novel femtosecond laser-based micromachining approaches for the fabrication of rotational-symmetric sapphire workpieces, specifically the generation of optical fibers by means of laser lathe of sapphire rods and the practical realization of windmill fibers. In addition, volume refractive index modification in planar sapphire substrates is presented to induce photonic crystal waveguides. The micromachined structures are comprehensively examined with respect to geometric fidelity, surface roughness, refractive index modification, and potential optical waveguiding properties. All micromachining approaches are done by means of frequency-doubled or frequency-tripled femtosecond laser radiation. Different laser optical setups including laser scanning head, spatial beam profilers including a spatial light modulator and axial rotatory movement of the specimen are employed for micro structuring and in-depth refractive index modifications. In particular for laser lathe, a sophisticated scanning pattern, in combination with an incremental axial rotatory movement of the specimen, allows for the precise diameter reduction of sapphire rods with 250 µm diameter to fibers with outer diameters of 25 µm. By supporting the workpiece with a V-groove fixture, multi-mode fibers with lengths up to 20 cm can be processed with an average surface roughness of 250 nm. Additionally, an adapted ablation scanning sequence enables the first practical demonstration of sapphire windmill fibers. Furthermore, using a spatial light modulator allows for the adaption of the laser propagation properties as to enable volume refractive index modifications with free-form arrangement. Hexagonal patterns of refractive index modifications surrounding a pristine waveguide core are fabricated and single-mode waveguiding at 1550 nm is verified. Finally, the possibility of integrating Bragg gratings into this photonic waveguide type is demonstrated
Sapphire is a robust and wear-resistant material. However, efficient and high-quality micromachining is still a challenge. This contribution demonstrates and discusses two novels, previously unreported approaches for femtosecond laser-based micromachining of rotational-symmetric sapphire workpieces, whereas both methods are in principal hybrids of laser scanning and laser turning or laser lathe. The first process, a combination of a sequential linear hatch pattern in parallel to the workpiece’s main axis with a defined incremental workpiece rotation, enables the fabrication of sapphire fibers with diameters of 50 µm over a length of 4.5 mm. Furthermore, sapphire specimens with a diameter of 25 µm over a length of 2 mm can be fabricated whereas an arithmetical mean height, i.e., Sa parameter, of 281 nm is achieved. The second process combines a constant workpiece feed and orthogonal scanning with incremental workpiece rotation. With this approach, workpiece length limitations of the first process are overcome and sapphire fibers with an average diameter of 90 µm over a length of 20 cm are manufactured. Again, the sapphire specimen exhibits a comparable surface roughness with an average Sa value of 249 nm over 20 cm. Based on the obtained results, the proposed manufacturing method paves an innovative and flexible, all laser-based way towards the fabrication or microstructuring of sapphire optical devices, and thus, a promising alternative to chemical processes.
This paper presents an extended control concept for automatic track guidance of industrial trucks in intralogistic systems. It is based on Reinforcement Learning (RL), a method of Artificial Intelligence (AI). The presented approach is able to adapt itself to different industrial truck variants and to the associated specific vehicle parameters. In order to avoid starting the whole
training of the controller for each truck variant from scratch, the training process is divided into two steps. In the first step, the controller is trained on a simplified linear model using parameters
of a nominal vehicle variant. Based on this, the control parameters are only fine-tuned in the second step using a more complex nonlinear model, representing the real industrial truck. In this
way, the controller is adapted to the actual truck variant and the corresponding parameter values. By using the nonlinear model, it can be ensured that the forklift’s dynamic is approximated
within the entire operating range, even at high steering angles. Moreover, the influence of the disturbance variable of the system (path curvature) is compensated by considering this a priori
knowledge within the control design. Therefore, the
Artificial Neural Networks (ANN) of the RL controller and the observation vector are suitably adjusted. In this way, the occurring path curvatures can be considered in both training steps and the control parameters can be optimized accordingly. Thus, the influence of the disturbance variable can be compensated, which significantly improves the control quality. In order to demonstrate this, the new approach is compared
to an RL control concept, which is not considering the disturbance variable and to a classical
two-degrees-of-freedom (2DoF) control approach.
Im Verbundprojekt KAnIS forscht die TH Aschaffenburg mit Linde Material Handling an neuen KI-basierten Algorithmen zur querdynamischen Fahrzeugführung von Flurförderzeugen. Ziel des Projekts ist die Entwicklung eines universell einsetzbaren Regelungskonzepts, das verschiedene Arten von Flurförderzeugen automatisch führt, im Betrieb auftretenden Fahrzeugparameterschwankungen gezielt Rechnung trägt und darüber hinaus auch den jeweiligen Fitnesszustand der Fahrzeuge berücksichtigt.
In Zeiten einer globalen Weltwirtschaft und einem von zunehmendem Wettbewerb geprägten Markt ist die Automatisierung logistischer Prozesse eine Voraussetzung für den Unternehmenserfolg. Vor allem die Steigerung der Produktivität und der Effizienz des innerbetrieblichen Materialflusses nimmt einen hohen Stellenwert ein. Mit dem Einsatz automatisch fahrender Flurförderzeuge (FFZ) lässt sich dies erreichen. Als Vision sollten jedoch nicht einzelne automatisch fahrende FFZ gelten. Ziel muss es sein, die Mitglieder einer heterogenen Logistikflotte miteinander zu vernetzen und eine Kommunikations- und Rechenplattform einzurichten. Dies bietet ein großes Potenzial im Hinblick auf die Auftragsplanung zur Verbesserung der Wirtschaftlichkeit sowie in den Bereichen Lokalisierung und Sicherheit zur Optimierung automatisch fahrender FFZ.
Ayahuasca is a blend of Amazonian plants that has been used for traditional medicine by
the inhabitants of this region for hundreds of years. Furthermore, this plant has been demonstrated to be a viable therapy for a variety of neurological and mental diseases. EEG experiments have found specific brain regions that changed significantly due to ayahuasca. Here,
we used an EEG dataset to investigate the ability to automatically detect changes in brain
activity using machine learning and complex networks. Machine learning was applied at
three different levels of data abstraction: (A) the raw EEG time series, (B) the correlation of
the EEG time series, and (C) the complex network measures calculated from (B). Further, at
the abstraction level of (C), we developed new measures of complex networks relating to
community detection. As a result, the machine learning method was able to automatically
detect changes in brain activity, with case (B) showing the highest accuracy (92%), followed
by (A) (88%) and (C) (83%), indicating that connectivity changes between brain regions are
more important for the detection of ayahuasca. The most activated areas were the frontal
and temporal lobe, which is consistent with the literature. F3 and PO4 were the most important brain connections, a significant new discovery for psychedelic literature. This connection may point to a cognitive process akin to face recognition in individuals during
ayahuasca-mediated visual hallucinations. Furthermore, closeness centrality and assortativity were the most important complex network measures. These two measures are also
associated with diseases such as Alzheimer’s disease, indicating a possible therapeutic
mechanism. Moreover, the new measures were crucial to the predictive model and suggested larger brain communities associated with the use of ayahuasca. This suggests that
the dissemination of information in functional brain networks is slower when this drug is
present. Overall, our methodology was able to automatically detect changes in brain activity
during ayahuasca consumption and interpret how these psychedelics alter brain networks,
as well as provide insights into their mechanisms of action
Das chinesische Normungssystem unterliegt seit Gründung der Volksrepublik 1949 einem kontinuierlichen Wandel. Mit der wirtschaftlichen Öffnung und wachsender Bedeutung am internationalen Handel wurde jedoch eine umfangreichere Modernisierung des chinesischen Normungssystems unausweichlich. Nachdem erste Versuche der Erneuerung des Normungssystems im Hauruckverfahren wenig Erfolg zeigten, geht China seit 2015 nun im Rahmen seiner Reformpläne für das Normungssystem einem
ganzheitlicheren Ansatz nach. Einem Ansatz, der den Anforderungen und Ansprüchen
einer führenden Wirtschaftsmacht in einem globalen Markt entspricht. Im Vergleich zu anderen führenden Normungsmächten wie Europa oder die USA gilt China als Nachzügler in der internationalen Normung. Das bietet jedoch den Vorteil, dass China aus den Erfahrungen anderer Nationen lernen und selbst ein Normungssystem etablieren kann, welches die besten Aspekte anderer Systeme aufgreift und gleichzeitig Chinas wirtschaftlichem Führungsanspruch gerecht wird.
Starting in 1951, on the 50th anniversary of the award of the first Nobel Prize for physics
to Wilhelm Conrad Röntgen, the Lord Mayor of the German city of Remscheid has annually awarded
Röntgen Medals to scientists who "in the broadest sense have made a special contribution to the
progress and dissemination of X-ray discoveries in the theoretical and applied sciences". The
Röntgen Medal has become highly recognized in the scientific world. To date, more than one
hundred scientists have received this honour. Through their chronology, this contribution presents a
"Who’s Who" of X-ray science and provides selected insights into their scientific work; with special
focus on the fields of X-ray optics and X-ray astronomy.
In 1895, Professor Wilhelm Conrad Röntgen detected a new kind of radiation that was able to penetrate
solid materials, which he called x-rays. In 1901 Röntgen received the first Nobel Prize in physics in honour of this
ground breaking discovery. The Deutsches Röntgen-Museum in Remscheid in Germany is the institution that
uniquely and comprehensively explores and documents the life and work of W. C. Röntgen and the impact of his
discovery. The museum’s location in Remscheid is not coincidental, with Röntgen’s birthplace only a short walk away from
its exhibits. Every visit to the museum amounts to a unique expedition through the worlds of medicine, science, and
technology. The museum’s emphasis on the diversity of Röntgen’s invention by a multilingual, multi-medial approach
enables all visitors to make their own personal discoveries. The Deutsches Röntgen-Museum in Remscheid is a mustsee
for x-ray scientists from anywhere in the world. This contribution provides an insight into the history of x-rays and
offers a guided tour of the Deutsches Röntgen-Museum and its exhibits.
Piezoelectrets fabricated from fluoroethylenepropylene (FEP)-foils have shown drastic increase of their piezoelectric
properties during the last decade. This led to the development of FEP-based energy harvesters, which are about to evolve
into a technology with a power-generation-capacity of milliwatt per square-centimeter at their resonance frequency. Recent
studies focus on piezoelectrets with solely negative charges, as they have a better charge stability and a better suitability for
implementation in rising technologies, like the internet of things (IOT) or portable electronics. With these developments
heading towards applications of piezoelectrets in the near future, there is an urgent need to also address the fabrication
process in terms of scalability, reproducibility and miniaturization. In this study, we firstly present a comprehensive review
of the literature for a deep insight into the research that has been done in the field of FEP-based piezoelectrets. For the first
time, we propose the employment of microsystem-technology and present a process for the fabrication of thermoformed
FEP piezoelectrets based on thermoforming SU-8 templates. Following this process, unipolar piezoelectrets were fabricated with air void dimensions in the range of 300–1000 lm in width and approx. 90 lm in height. For samples with a void
size of 1000 lm, a d33-coefficient up to 26,508 pC/N has been achieved, depending on the applied seismic mass. Finally,
the properties as energy harvester were characterized. At the best, an electrical power output of 0.51 mW was achieved for
an acceleration of 1 g with a seismic mass of 101 g. Such piezoelectrets with highly defined dimensions show good
energy output in relation to volume, with high potential for widespread applications.
Functional connectivity and convolutional neural networks for automatic classification of EEG data
(2022)
Objective: Tau ablation has a protective effect in epilepsy due to inhibition of the hyperexcitability/hypersynchrony. Protection may also occur in transgenic models of Alzheimer's disease by reducing the epileptic activity and normalizing the excitation/inhibition imbalance. However, it is difficult to determine the exact functions of tau, because tau knockout (tauKO) brain networks exhibit elusive phenotypes. In this study, we aimed to further explore the physiological role of tau using brain network remodeling. Approach: The effect of tau ablation was investigated in hippocampal-entorhinal slice co-cultures during network remodeling. We recorded the spontaneous extracellular neuronal activity over two weeks in single-slice cultures and co-cultures from control and tauKO mice. We compared the burst parameters and applied concepts and analytical tools intended for the analysis of the network synchrony and connectivity. Main results: Comparison of the control and tauKO co-cultures revealed that tau ablation had an anti-synchrony effect on the hippocampal-entorhinal two-slice networks at late stages of culture, in line with the literature. Differences were also found between the single-slice and co-culture conditions, which indicated that tau ablation had differential effects at the sub-network scale. For instance, tau ablation was found to have an anti-synchrony effect on the co-cultured hippocampal slices throughout the culture, possibly due to a reduction in the excitation/inhibition ratio. Conversely, tau ablation led to increased synchrony in the entorhinal slices at early stages of the co-culture, possibly due to homogenization of the connectivity distribution. Significance: The new methodology presented here proved useful for investigating the role of tau in the remodeling of complex brain-derived neural networks. The results confirm previous findings and hypotheses concerning the effects of tau ablation on neural networks. Moreover, the results suggest, for the first time, that tau has multifaceted roles that vary in different brain sub-networks.
In recent years, there has been an increasing interest in electrically conductive hydrogels for a wide range of biomedical applications, like tissue engineering or biosensors. In this study, we present a cost-effective conductive hydrogel based on alginate and graphene nanoplatelets for extrusion-based bioprinters. The hydrogel is prepared under ambient conditions avoiding high temperatures detrimental for cell culture environments. Investigation of the hydrogel revealed a conductivity of up to 7.5 S/cm, depending on the ratio of platelets. Furthermore, in vitro tests with human embyronic kidney cells - as an example cell type - showed good adhesion of the cells to the surface of the conductive hydrogel. Electrochemical measurements revealed a low electrode impedance which is desirable for the extracellular recording, but also low electrode capacitance, which is unfavorable for electrical stimulation purposes. Therefore, future experiments with the graphene nanoplatelets-based hydrogels will focus on electrodes for biosensors and extracellular recordings of neurons or cardiac myocytes.
Mental disorders are among the leading causes of disability worldwide. The first step in treating
these conditions is to obtain an accurate diagnosis. Machine learning algorithms can provide a
possible solution to this problem, as we describe in this work. We present a method for the
automatic diagnosis of mental disorders based on the matrix of connections obtained from EEG
time series and deep learning. We show that our approach can classify patients with Alzheimer’s
disease and schizophrenia with a high level of accuracy. The comparison with the traditional cases,
that use raw EEG time series, shows that our method provides the highest precision. Therefore, the
application of deep neural networks on data from brain connections is a very promising method
for the diagnosis of neurological disorders.
This paper presents an extension of a self-learning control concept for automatic track guidance of industrial trucks in intralogistic systems. The presented approach is based on Reinforcement Learning (RL), a method of Artificial Intelligence (AI) and is able to adapt itself to different
industrial truck variants and the associated specific vehicle parameters. Moreover, time-variant parameters during operation, such as the vehicle's velocity are taken into account. In order to consider the existing a priori knowledge of the controlled system and to avoid starting
the whole training process of the controller for each truck variant from scratch, the training process is divided into two steps. In the first step, the controller is trained on a model using
parameters of a nominal vehicle variant. Based on this, the control parameters are only finetuned in the second step. In this way the controller is adapted to the actual truck variant and the corresponding parameter values. In order to take into account the time-variant vehicle parameters during operation, the Artificial Neural Networks (ANN) of the RL controller and the observation vector are suitably extended. In this way, the varying speed can be considered in both training steps and the control parameters can be optimized accordingly. Thus, in case of
the investigated scenarios a stable control loop behavior can be guaranteed for the entire speed range of industrial trucks. In order to demonstrate this, the new approach is compared with a
RL control concept, not considering time-variant parameters.
This paper presents a new control concept for automatic track guidance of industrial trucks in intralogistic systems. It is based on Reinforcement Learning (RL), a method of Artificial Intelligence (AI). The presented approach is able to adapt itself to different industrial truck variants and to the associated specific vehicle parameters. In order to avoid starting the whole training of the controller for each truck variant from scratch, the training process is divided into two steps. In the first step, the controller is trained on a model using parameters of a nominal vehicle variant. Based on this, the control parameters are only fine-tuned in the second step. In this way the controller is adapted to the actual truck variant and the corresponding parameter values. Moreover, the influence of the disturbance variable of the system (path curvature) is compensated by considering this a priori knowledge within the control design. Therefore, the Artificial Neural Networks (ANN) of the RL controller and the observation vector are suitably adjusted. In this way, the occurring path curvatures can be considered in both training steps and the control parameters can be optimized accordingly. Thus, the influence of the disturbance variable can be compensated, which significanlty improves the control quality. In order to demonstrate this, the new approach is compared to a RL control concept, not considering the disturbance variable and to a classical two-degrees-of-freedom (2DoF) control approach.
Lobster-eye type X-ray telescopes use reflecting plano mirrors under grazing incidence and can observe a large field of view. As part of a Bavarian-Czech cooperation, two telescopes were build, equipped with mirrors coated with gold and iridium. Their X-ray characterization was carried out at the PANTER test facility, which simulates parallel starlight incident on the telescopes. The telescopes have an angular resolution of about 4 arc minutes in X-rays and a focal length of about 2 meters. The used X-ray mirrors reflect and focus visible light as well; their functionality in the optical regime was checked in laboratory tests. Now another test campaign will be carried out to examine the telescope resolution for real objects of the visible night sky and the imaging properties for star constellations.
The effective area is one of the main telescope parameters when justifying real space application. We discuss the estimation of the effective collecting area of an X-ray telescope by two different methods, an analytical method and a simulation algorithm, and then compare the results. The Lobster Eye type telescopes considered here are designed for rocket experiments and CubeSat flights.
Das Edelmetall Iridium ist hart; extrem dicht; thermisch, mechanisch und chemisch stabil; weist eine hohe Reflektivität im mittleren und fernen Infrarot auf und hat eine hohe Beständigkeit gegenüber Umwelteinflüssen - auch ohne weitere Schutzschichten. Es wurden die komplexen Brechungsindizes für Iridium-Spiegelbeschichtungen bestimmt, welche vorhandene Literaturwerte ergänzen.
Upgrade of a laboratory X-ray diffractometer to extend its operating range towards soft energies
(2022)
The optical properties of X-ray mirror samples are commonly measured using diffractometers based on laboratory sources; like the Bede D1 diffractometer operating at INAF-OAB. This instrument can generate a collimated X-ray beam up to 60 keV, even though the most interesting energy region for x-ray astronomy applications is usually below 10 keV. In the softest part of this range (below 6 keV), high X-ray absorption in air hinders a full and precise characterization of optical components. In this work, we present an upgrade of the Bede D1 diffractometer that extends the operative range of the
instrument below 6 keV; this is done by maximizing the flux at lowest energies and by reducing absorption by means of a helium-rich atmosphere.
The upgraded instrument will be used for the tests of X-ray mirrors with innovative soft X-ray coatings, with potential application to the next generation X-ray telescopes (such as ATHENA and eXTP).
Röntgenteleskop-Funktionstests durch Beobachtung astronomischer Objekte am sichtbaren Nachthimmel
(2022)
Lobster-Eye-Röntgenteleskope nutzen reflektierende Planspiegel unter streifendem Einfall und zeichnen sich durch ein großes Beobachtungsfeld aus. Die Spiegel reflektieren auch sichtbare Strahlung hervorragend. Nach Röntgen-messungen im Labor wurden nun weitere Tests durchgeführt, um die Abbildungs-eigenschaften mit realen Objekten des sichtbaren Himmels zu untersuchen.
We report on milling and tool wear characteristics of hybrid additive manufacturing comprising laser powder bed fusion and in situ high-speed milling, a particular process in which the cutter mills inside the powder bed without any cooling lubricant being applicable. Flank wear is found to be the dominant wear characteristic with its temporal evolution over utilization period revealing the typical s-shaped dependence. The flank wear land width is measured by microscopy and correlated to the achievable surface roughness of milled 3D-printed parts, showing that for flank wear levels up to 100 μm a superior surface roughness below 3 μm is accessible for hybrid additive manufacturing. Further, based on this correlation recommended tool, life scenarios can be deduced. In addition, by optimizing the finishing tool start position and the number of afore-built layers, the milling process is improved with respect to the maximum millable angle for undercut surfaces of 3D-printed parts to 30° for the roughing process and to 40° for the entire machining process including finishing
Abstract: This contribution demonstrates photonic crystal waveguides generated within bulk planar sapphire substrates. A femtosecond laser is used to modify the refractive index in a hexagonal pattern around the pristine waveguide core. Near-field measurements reveal single-mode behavior at a wavelength of 1550 nm and the possibility to adapt the mode-field diameter. Based on farfield examinations, the effective refractive index contrast between the pristine waveguide core and depressed cladding is estimated to 3x10-4. Additionally, Bragg gratings are generated within the waveguide core. Due to the inherent birefringence of Al2O3, the gratings exhibit two distinct wavelengths of main reflection. Each reflection peak exhibits a narrow spectral full width at a half maximum of 130 pm and can be selectively addressed by exciting the birefringent waveguide with appropriately polarized light. Furthermore, a waveguide attenuation of 1 dB cm-1 is determined.
Design Rules for Hybrid Additive Manufacturing Combining Selective Laser Melting and Micromilling
(2021)
We report on a comprehensive study to evaluate fundamental properties of a hybrid
manufacturing approach, combining selective laser melting and high speed milling, and to characterize
typical geometrical features and conclude on a catalogue of design rules. As for any additive
manufacturing approach, the understanding of the machine properties and the process behaviour as
well as such a selection guide is of upmost importance to foster the implementation of new machining
concepts and support design engineers. Geometrical accuracy between digitally designed and
physically realized parts made of maraging steel and dimensional limits are analyzed by stripe line
projection. In particular, we identify design rules for numerous basic geometric elements like walls,
cylinders, angles, inclinations, overhangs, notches, inner and outer radii of spheres, chamfers in build
direction, and holes of different shape, respectively, as being manufactured by the hybrid approach
and compare them to sole selective laser melting. While the cutting tool defines the manufacturability
of, e.g., edges and corners, the milling itself improves the surface roughness to Ra < 2 µm. Thus,
the given advantages of this hybrid process, e.g., space-resolved and custom-designed roughness
and the superior geometrical accuracy are evaluated. Finally, we exemplify the potential of this
particular promising hybrid approach by demonstrating an injection mold with a conformal cooling
for a charge socket for an electro mobile
For the past four decades, ZERODUR® glass ceramics has flown on many satellites including the prominent
space missions METEOSAT, Hubble Space Telescope, CHANDRA, and LISA pathfinder. Firstly, this unique
material is chosen as mirror substrate for high precision optics due to its extreme thermal stability. Its near-zero thermal expansion over a wide temperature range of several tens of Kelvin is homogenous within the entire
volume. This enables control of the ZERODUR®’s surface profile at the 10-picometer level. SCHOTT has conducted comprehensive material characteristics studies on the mechanical properties and the radiation environment effects experienced in realistic orbits to define the suitability of ZERODUR® to survive both high loads during launch and to support long-term missions, respectively.
Besides these advantageous material properties, this glass-ceramics can be extremely light-weighted by
precision grinding enabled by the new SCHOTT competence center for machining and metrology. In this paper,
we will continue to trace the recent developments of ZERODUR® glass ceramics as space material in the context
of selected missions flown since 2009 and those anticipated. Major milestones such as the LISA pathfinder
mission are discussed. Furthermore, we outline the viable use of ZERODUR® for great observatory
architectures for IR/O/UV spaceborne telescopes.
The objective of this paper is to supplement an earlier review of the use of ZERODUR® for space applications
in the past decade and to summarize the latest progress and results of material studies toward very efficient
production capabilities for high-performance light-weighted mirror substrates.
The massive shift to working from home during the Covid-19 pandemic triggered discussions about its potential impact on the future demand for office space and the risk it poses to the performance of office markets. Against this background, the goal of this paper is to investigate the link between working from home and the evolution of key indicators of office occupier markets across Europe over the past three decades. Based on the data from Eurostat and CBRE, the paper uses panel regression to investigate the temporal as well as cross-sectional relationships between the share of the workforce working from home and office rents and vacancy rates in major cities. The results are interesting in several ways. Firstly, changes in the share of employees working from home did not appear to have any significant impact on the evolution of rents or vacancy rates over time. However, occasional homeworking was significant in explaining cross-sectional differences in office market indicators. Moreover, contrary to the initial expectations, higher share of employees occasionally working from home appeared to be associated with stronger performance of the respective office market. As explanation, the paper proposes a hypothesis that this was due to working from home being only one aspect of broader changes in the office work environment and related socio-economic trends that had a net beneficial effect on office occupier markets. Although the results refer to historical developments and may not be fully applicable to the current context of the pandemic, they highlight the need to consider working from home in a broader perspective of office occupier trends and ways of working.
Manipulation von Abgaswerten
(2021)
Dieses Buch stellt Hintergründe zum Abgasskandal dar, z. B. welche Schadstoffe kritisch sind, wie Motorsteuergeräte, Abgasrückführung und Abgasnachbehandlung funktionieren, wie Manipulationen auf dem Prüfstand möglich sind, mit welchen Fahrzyklen getestet wird und in welchem rechtlichen und politischen Umfeld dies lange Zeit geschehen konnte. Es werden Maßnahmen vorgestellt, mit denen Fahrzeuge auch real Grenzwerte einhalten können und wie Manipulationen zukünftig rechtlich und politisch verhindert werden können. Dem Leser werden durch Literaturhinweise zusätzliche Details erschlossen.
Direktinvestitionen
(2001)
Highly reflective metal coatings are essential for numerous optical elements. Established mirror coatings made of silver (Ag) and gold (Au) offer high and broadband self-reflection in the infrared (IR) spectral range but are susceptible to
environmental influences and mechanical stress without suitable protective layers. In the long-wavelength spectral range, in particular, the absorption bands of these protective layers partially reduce the high mirror reflectivity again. However,
the noble metal iridium (Ir) is hard, extremely dense, and thermally, mechanically, and chemically stable. Iridium
provides a similarly high reflectivity in the mid (MIR) and far-infrared (FIR) spectral range, as silver and gold, and high resistance to environmental influences - even without protective layers. In this paper, the different deposition processes, as well as the optical and structural properties of iridium mirror coatings fabricated by atomic layer deposition (ALD)
and by magnetron sputtering (MS), are presented and compared with each other. The complex refractive indices for ALD and MS deposited iridium mirror coatings were determined for wavelengths from 200 nm to 20 μm, complementing the existing literature values. We demonstrate that iridium mirror coatings offer a high and broadband reflectivity from the mid to far-infrared spectral range. In contrast to established – protected – silver and gold mirror coatings, the iridium
coatings are environmentally durable and thermally stable up to 600 °C, even without protective layers. Therefore, as an interesting mirror coating material, iridium has the potential for special applications in infrared astronomy and probably
also for industrial instruments.
We address the problem of estimation the sensitivity of astronomical X-ray telescopes of Lobster Eye type , with emphasis on calculation of effective areas for telescopes designed for rocket and CubeSat flights. This parameter is one of the principal parameters when justifying the real space application. Indeed, the larger the effective area is, the more efficient the optical system is, able to provide images of fainter and more distant celestial targets. We discuss the estimation of the effective collecting area of a X-ray telescope by two different methods and then compare the results: the analytical method and then the simulation algorithm.
Hochreflektierende Metallbeschichtungen sind essenziell für zahlreiche optische Elemente. Bewährte Spiegelbeschichtungen aus Silber und Gold bieten eine hohe und breitbandige Eigenreflexion im infraroten Spektralbereich, sind ohne geeignete Schutzschichten jedoch anfällig gegenüber Umwelteinflüssen und mechanischer Beanspruchung. Insbesondere im langwelligen Spektralbereich verringern die Absorptionsbanden dieser Schutzschichten teilweise die hohe Spiegelreflektivität wieder. Das Edelmetall Iridium (Ir) ist hart; extrem dicht; thermisch, mechanisch und chemisch stabil; weist eine ähnlich hohe Reflektivität im mittleren und fernen Infrarot, wie Silber und Gold, auf und hat zusätzlich eine hohe Beständigkeit gegenüber Umwelteinflüssen - auch ohne Schutzschichten. In diesem Beitrag werden die optischen und strukturellen Eigenschaften von Iridium-Spiegelbeschichtungen, welche mittels Atomlagenabscheidung (ALD) und DC-Magnetron-Sputtern hergestellt wurden, vorgestellt und miteinander verglichen. Die komplexen Brechungsindizes für ALD-erzeugte und gesputterte Iridium-Spiegelbeschichtungen wurden für Wellenlängen von 200 nm bis 20 μm bestimmt, welche nun bereits vorhandene Literaturwerte ergänzen.
In this study, we analyse the advantageous effects of neural networks in combination with wavelet functions on the performance of financial market predictions. We implement different approaches in multiple experiments and test their predictive abilities with different financial time series. We demonstrate experimentally that both wavelet neural networks and neural networks with data pre-processed by wavelets outperform classical network topologies. However, the precision of conducted forecasts implementing neural network algorithms still propose potential for further refinement and enhancement. Hence, we discuss our findings, comparisons with “buy-and-hold” strategies and ethical considerations critically and elaborate on future prospects.
Normung galt lange als ein rein technisches Thema für ausgewiesene Spezialisten. Neuerdings erhält das Thema zusätzliche Aufmerksamkeit durch Vertreter aus industrie- und geopolitischen Fachkreisen, insbesondere aufgrund des Entwicklungsprojekts zur Seidenstraße. Die Autorinnen skizzieren den Erneuerungsbedarf für die Normungswelt und fordern mehr Innovation, um den wachsenden Herausforderungen in der internationalen Normung entgegen zu treten.
Advanced Control Methods for High Performance Dual Two-Level Inverter for Traction Application
(2021)
The topology of the dual two-level inverter in combination with an electrical machine with open-end winding is an optimal
solution for the realization of high requirements from the automotive sector for high-performance traction drives. In this
publication, methods for extending the operating range and improving output voltage and current quality are presented
for synchronous as well as asynchronous PWM methods for the entire operating range for this system configuration.
Emphasis is placed on symmetrical power sharing between the inverters to maximize the power range. Optimal integration
of the system is achieved by the topology-related possibility of DC fast charging of the energy storages from a DC grid
without an additional charging unit.
This paper presents a new self-learning control scheme for lateral track guidance of industrial trucks using artificial intelligence. It is an universally applicable lateral dynamic control concept which is able to adapt itself to different truck variants. Moreover it shall consider vehicle parameter variations that occur during operation, such as the load dependent change of vehicle mass and moment of inertia. The proposed approach uses Reinforcement Learning. In order to reduce the training effort, a new concept is realized, taking into account a priori knowledge of vehicle behavior. Its fundamental idea consists of dividing the training process into two steps. In the first step the controller will be pre-trained on basis of a nominal model representing a priori knowledge of lateral dynamic vehicle behavior. Since this model is derived for an industrial truck with average vehicle parameter values, a fine tuning of the control parameters has to be performed in the second step. In this way the controller is adapted to the actual truck variant and the corresponding vehicle parameter values. In order to demonstrate the efficiency of the proposed control scheme, the simulation results given in this paper are compared to the closed loop behavior using standard LQR.
This experimental study analyzes how a key factor, information load, influences decision making in escalation situations, i.e., in situations in which decision mak- ers reinvest further resources in a losing course of action, even when accounting information indicates that the project is performing poorly and should be discontin- ued. This study synthesizes prior escalation research with information overload and investigates how different levels of information load influence the escalation of com- mitment. Our findings reveal a U-shaped effect of information load: When decision makers face negative feedback, a higher information load mitigates the escalation tendency up to a certain point. However, beyond this point, more information rein- forces the escalation tendency. Moreover, we find that the type of feedback affects self-justification, and we find a negative and significant interaction between informa- tion load and self-justification in negative-feedback cases. Thus, studies investigat- ing escalation of commitment should control for self-justification and information load when utilizing high levels of information load. Finally, in the positive-feedback condition, higher information load encourages decision makers to continue promis- ing courses of action, i.e., increases decision-making performance.
Abstract: Like many service industries, the financial industry is largely characterized
by administrative and back-office processes and distinguished by a broad systems
landscape with a high proportion of legacy systems. Missing interfaces between information
systems, user interfaces, or web applications often require many manual
activities. As banks are often functionally organized into traditional departments, a
process-oriented organizational structure is rarely in place. The financial industry
therefore offers enormous potential for the use of robotic process automation (RPA)
and the raising of potential benefits such as process-related cost savings, time reductions,
and quality improvements.
The aim of this chapter is to describe the tremendous opportunities that the use of
RPA technology offers to the financial industry and to explain how these opportunities
can be realized. Therefore, we start by explaining the challenges that progressive digitalization
poses to the industry and how RPA, but also more advanced technologies
(that work not only rule-based but also define own rules), such as artificial intelligence,
can help to overcome them. As well as providing an overview of the various
applications of RPA in the financial industry, we also provide a comprehensive case
study of a relevant practical application
Metallic coatings are essential for numerous optical systems due to their high and broadband refl ectivity in the infrared spectral range. In contrast to well-established (protected)silver and gold mirror coatings, iridium is environmentally durable, referring to ISO 9211-3 and thermally stable up to 600 °C even without protective layers, as demonstrated. Additionally,the optical and related structural properties of atomic layer deposited (ALD) and magnetron sputtered (MS) Ir coatings were investigated using spectrophotometry, FTIR, ellipsometry, WLI, AFM, XRR, XRD, SEM, and electrical resistivity measurements. The properties of Ir ALD and Ir MS coatings diff er due to their topography and microstructure.
Metallic coatings are essential for numerous optical systems due to their high and broadband refl ectivity in the infrared spectral range. In contrast to well-established (protected)silver and gold mirror coatings, iridium is environmentally durable, referring to ISO 9211-3 and thermally stable up to 600 °C even without protective layers, as demonstrated. Additionally,the optical and related structural properties of atomic layer deposited (ALD) and magnetron sputtered (MS) Ir coatings were investigated using spectrophotometry, FTIR, ellipsometry, WLI,AFM, XRR, XRD, SEM, and electrical resistivity measurements. The properties of Ir ALD and Ir MS coatings diff er due to their topography and microstructure.
Increasing data transmission rates and bandwidth both belong to the challenges of the development of high-performance wireless communication systems. Multi-channel communication systems commonly use several narrowband power amplifiers each one for a single communication channel. Lossy couplers are needed both to separate the different channels from each other at the amplifiers input and to combine the amplified signals on each channel at the output. This approach depicts a poor efficiency and is limited to a few number of channels since each channel duplication involves 3 dB losses due to couplers.
Alternatively, broadband radio frequency power amplifiers ensuring the simultaneous transmission of several carriers on a wide frequency range contribute to increase the cost and resource efficiency of transceivers in wireless communication systems. Gain flatness, a high output power, and low power levels of second and third order harmonics are required on the whole operating frequency range of the power amplifier in multi-carrier communication systems since overtones will degrade the quality of the communication.
The present work investigates the performances of a broadband push-pull power amplifier based on LDMOS transistors, the input matching network using a 8:1 transmission line transformer. For the first time investigations on harmonic distortions of the amplified signal when using a transformer with 8:1 impedance transformation ratio are presented. Characterisation of the power amplifiers performances is focused on gain flatness, output power, harmonic distortions and efficiency at 110 W.
Chaoticity Versus Stochasticity in Financial Markets: Are Daily S&P 500 Return Dynamics Chaotic?
(2022)
In this study, we empirically show the dynamics of daily wavelet-filtered (denoised) S&P 500 returns (2000–2020) to consist of an almost equally divided combination of stochastic and deterministic chaos, rendering the series unpredictable after expiration of the Lyapunov time, resulting in futile forecasting attempts. We achieve a clear distinction of the true nature of the underlying time series dynamics by applying a novel and combinatory chaos analysis framework comparing the wavelet-filtered S&P 500 returns with respective surrogate datasets, Brownian motion returns and a Lorenz system realisation. Furthermore, we are the first to show the strange attractor of especially the daily-frequented S&P 500 return system graphically via Takens´ embedding and by spectral embedding in combination with Laplacian Eigenmaps. Finally, we critically discuss implications and future prospects in terms of financial forecasting.
Enterprise social media has been found to be a curse and a blessing at the same time. ESM has been reported to lead to unproductive ‘games of visibility’ and ‘exhibitionism’, while it has been also found to enable productive outcomes related to knowledge work and product innovation, the latter being the main reason for its wide-spread adoption. We argue that decisions to use ESM as a control instrument are not made in isolation, but as part of a set of complementary choices. We provide arguments and empirical evidence that the use of ESM as a control instrument in organizations complements the use of subjective evaluations of non-task related performance (SPE). We also show that firms that face high ESM employee concerns, have a stronger complementarity between ESM use and SPE. Additional analyses show that ESM use and performance-based pay (PBP) are also complements. Together the results imply that management control system configuration changes with the employment of ESM.
Aluminium evaporation is still the standard solution for reflective coatings of large astronomical mirrors. Silver and gold are also used in specific cases depending on the targeted wavelength. This study characterized different metallic coatings - including unusual ones like sputtered iridium - to identify the most suitable mirror coating for the spectral range from ultraviolet to infrared wavelengths.
High reflectivity grazing incidence mirrors of astronomical X-ray telescopes are usually coated with thin layers of iridium, gold, or platinum. Due to a series of absorption edges, these noble metals have low reflectivity in the 2 - 4 keV band. We present the development of innovative material combinations using chromium and an additional layer of polydopamine for enhanced reflectivity X-ray coatings.
Im Rahmen einer bayerisch-tschechischen Kooperation entstanden zwei Röntgenteleskope, bestückt mit Gold- und Iridium-beschichteten Planspiegeln. Deren Charakterisierung erfolgte an der Röntgentestanlage PANTER, welche parallel auf die Teleskope einfallendes Sternenlicht simuliert. Die Teleskope haben eine Winkelauflösung von ca. 4 Bogenminuten und eine Brennweite von rund 2 Metern.
Der unentgeltliche Zuwendungsnießbrauch an GmbH-Beteiligungen ist eine häufig genutzte Gestaltung, die auf die Versorgung von Angehörigen im Rahmen der vorweggenommenen Erbfolge abzielt. Aus wirtschaftlicher Sicht soll mit der Bestellung Nicht-Gesellschaftern eine regelmäßige Einkunftsquelle verschafft werden; daneben gilt es, bei den Beteiligten ertragsteuerliche, erbschaft- und schenkungsteuerliche Privilegien zu nutzen. Konkret geht es und die Ausschöpfung von Progressionsvorteilen und Freibeträgen. Grundsätzlich bleibt aber festzuhalten, dass die Bestellung eines Zuwendungsnießbrauchs an GmbH-Anteilen nach wie vor mit erheblichen rechtlichen und steuerlichen Unsicherheiten behaftet ist.
The European Union-funded Advanced Superconducting Motor Experimental Demonstrator (ASuMED) project started in May 2017 with the purpose of demonstrating the benefits of a new, fully superconducting motor for reaching the targets established by the Flightpath 2050 plan. The project aims at a motor power density of 20 kW kg−1 using
a high-temperature superconducting (HTS) stator. The rotor will use HTS stacks operating like permanent magnets. A highly efficient cryostat for the motor combined with an integrated cryogenic cooling system and associated power converter will be used. This article provides a general overview of the prototype that is currently being assembled and that will be tested soon.
Combustion efficiency of iridium coated pellets for environmentally friendly space propulsion
(2021)
Most of the satellite engines still uses critical fuels such as hydrazine, which is chemically aggressive, toxic and carcinogenic. New developments for satellite engines try to avoid such critical propellants. One promising approach is the usage of rocket-grade hydrogen peroxide [H2O2] in mono- and bipropellant driven rocket engines. Catalysts in the rocket engines convert the hydrogen peroxide by an exothermic catalytic reaction; the resulting hot gases oxygen and water vapor provide the thrust. Currently used catalysts are, for example, Al2O3 pellets impregnated with platinum.
Within a joint research project of Aschaffenburg University and the German Aerospace Center new catalysts are developed. They consist of ceramic pellets coated with iridium using the magnetron sputtering process. Thereby the surface structure of the iridium layers strongly depends on the used sputtering process conditions [1]. After optimization of the sputtering parameters, it was demonstrated in laboratory experiments that the catalytic effect (measured by the volume of released gas) can be increased by a factor of four compared to platinum impregnated pellets [2].
In first hot firing tests at the test bench complex M11 at the DLR- Institute of Space Propulsion, these new, iridium-based catalysts have been used in a model combustion chamber for hydrogen peroxide decomposition. For this purpose, the reaction chamber was filled with iridium pellets in the high-altitude simulation chamber of the M11.2 test bench. The model chamber was equipped with numerous measuring devices like temperature and pressure sensors (e.g. Tcat, pcat). With the help of the mass flow and the herein obtained data, performance characteristics of the propellant system were accessible. High-concentrated hydrogen peroxide was used in the experiments as monopropellant (~ 87-wt.% H2O2). During the experiments, the combustion chamber was operated in pulse mode and in continuous mode. Aim of this campaign called MoCa (“Monopropellant Catalytic Demonstrator”) is the demonstration of functionality and the performance evaluation of this iridium-based monopropellant system. Recent experimental results will be presented.
References:
[1] A. Büttner et al., Thin Solid Films 2018, 662: 41–46
[2] M. Stollenwerk et al., Journal of Materials Science 2021, 56(16), 9974-9984
Recent progress in nanosatellite technologies allows to consider innovative new CubeSat missions for scientific purposes. We present and evaluate the design of a small and cost effective CubeSat mission to monitor lunar meteoroid impacts by detecting their optical flashes. The poster summarizes the results of a comprehensive survey of past and recent ground based and satellite based projects focussing on lunar impact monitoring and discusses important aspects of the proposed mission and various alternatives for their solutions. Several spacecraft orbits around Moon and their usefulness for lunar impact observation are studied. In addition, we discuss the environmental risks and challenges, which such spacecraft needs to face, mainly thermal management and radiation tolerance. Finally, we present and discuss the design an optical camera suitable to detect meteoroid impacts on the lunar surface.
With ground based optical telescopes astronomers observe celestial objects over a wide spectral range. As usually three or even more reflections at telescope mirrors are involved, good reflection properties of the mirror coatings are important. The aluminum evaporation technique has been - and is still - the standard solution for the reflective coatings of large astronomical mirrors. Such coatings have excellent reflectivity in the ultraviolet and in the visible, but perform poorly in the infrared. Silver is the metal having highest reflectivity for wavelengths longward of 400 nm, but isn´t the best choice for reflectivity in the ultraviolet and for blue light. To avoid degradation by oxidation, durable silver coatings need to be protected by transmitting overcoating layers. In the presented study, different metallic coatings – including unusual ones like sputtered iridium - are characterized to identify a coating that is most suitable for the spectral range from ultraviolet to infrared. Experimental results are compared to simulations based on the complex refractive indices of these materials. Thereby dependence of incidence angle and polarization is also considered.
Im Rahmen einer bayerisch-tschechischen Kooperation entstanden zwei mechanisch baugleiche Röntgenteleskope, bestückt mit Gold- und Iridium-beschichteten Planspiegeln. Die Charakterisierung der nach dem ägyptischen Gott HORUS benannten Teleskope erfolgte an der Röntgentestanlage PANTER des Max-Plack-Instituts für extraterrestrische Physik. Diese Vakuum-Testanlage simuliert parallel auf die Teleskope einfallendes Sternenlicht, wobei hier die Strahlung aus einer Röntgenquelle in 120 Metern Abstand stammt. Die Messungen selbst fanden in einer daran angebauten 12 Meter langen Testkammer von 3,5 Metern Durchmesser statt. Im März 2021 sahen die HORUS-Teleskope zum erstem Mal Röntgenlicht. Während der Testkampagne von ca. 54 Stunden Dauer wurden 536 Einzelmessungen an den beiden Teleskopen durchgeführt, bei denen Photonenenergien und Einfallswinkel variiert wurden. Von einer empfindlichen CCD-Kamera, einem Prototyp der eROSITA-Satellitenkamera, wurden hierbei insgesamt 11.153.574 Röntgenphotonen individuell detektiert, analysiert und digital verarbeitet. Die beiden Weitwinkel-Röntgenteleskope haben eine Winkelauflösung von circa 4 Bogenminuten und eine Brennweite von rund zwei Metern.
X-ray telescopes usually operate in space and are quite different from astronomical telescopes for visible light. For normal angles of incidence, optical light is reflected on the mirror surface, whereas X-rays are either transmitted or absorbed. However, also high reflectivity X-rays mirrors are possible, when the incident rays direction is almost parallel to the mirror surface. Such grazing incidence mirrors are usually coated with thin layers of precious metals like iridium, gold or platinum, as this result in high X-ray reflectivity. These noble metals offer a wide range of reflection up to high photon energies, but, due to a series of absorption edges, have low reflectivity in the 2 - 4 keV band and below. This contribution presents the development of innovative material combinations based on thin layers of iridium and chromium, followed by an additional layer of carbon-based materials. We also discuss corresponding production methods (like dip coating) for enhanced reflectivity mirror coatings of future X-ray telescopes.